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Old 02-29-2012, 09:58 PM   #1
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10" high attic, flat roof - best way to insulate


My bathroom is always about 10-15 degrees colder than the rest of the house. I FINALLY decided to cut a hole in the ceiling to see what I got. 2x10 rafters/joists from wall to wall, then the roof sheathing is on top (no slope in the roof, just flat on the bathroom). I was considering just stuffing in unfaced r-30 and calling it a day, but wasn't sure if I need to allow for any ventilation or not for this type of attic/roof (I'd rather fill it up entirely if I could, as I live in northern maryland).

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Old 02-29-2012, 11:20 PM   #2
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10" high attic, flat roof - best way to insulate


I would think you should put in some ventilation baffles, and vented soffits at either end of the rafter bays, if possible.
You could fir the rafters a couple inches for max insulation also, if possible.


Last edited by titanoman; 02-29-2012 at 11:23 PM.
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Old 03-01-2012, 01:08 AM   #3
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10" high attic, flat roof - best way to insulate


you absolutely need ventilation, unless you are going to get the lid spray foamed and have the whole place conditioned. for that, i'd do some reading on buildingscience.com for details, as that may be a bit trickier over a bathroom. if you don't foam it, air seal when you button the place up. how are you going to access the area? remove ceiling, or roof? if you stuff in batts, don't use fiberglass. rock wool is a better material.
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Old 03-01-2012, 07:29 AM   #4
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10" high attic, flat roof - best way to insulate


Is this an add on bathroom (in other words, does the roof butt up against a high wall)? If so it will be difficult to ventilate properly without getting a hold of a roofer who specializes in flat roofing (if they want to slap some goop on the roof, they DO NOT specialize in flat roofing). A bit more detail would be required.

I would be hesitant to use spray foam, as it is not a question of if the roof will leak, but when, and when it does spray foam could hide the problem from you long enough to cause serious damage. Being a bathroom (aka high moisture) ventilation and a proper vapour barrier are a must.
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Old 03-01-2012, 11:17 PM   #5
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10" high attic, flat roof - best way to insulate


Read on: http://www.buildingscience.com/docum...+in+flat+attic

http://publicecodes.citation.com/ico...006_par003.htm

Find your Zone: http://publicecodes.citation.com/ico...001_par001.htm

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Old 03-02-2012, 07:29 AM   #6
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10" high attic, flat roof - best way to insulate


Pictures will help here...

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